The invention pertains to intermediate material for the production of electrical contacts by the bonding of this material by resistance heating to an electrically conductive contact carrier strip consisting essentially of copper. The intermediate material is in the form of a metal strip with a contact area. The bottom surface of this strip, i.e., the surface which can be bonded to the contact carrier strip, is coated with a material which consists essentially of silver, the melting point of the coating material being below the melting point of the metal strip. The invention also pertains to a process for the production of the intermediate material and to semifinished products for electrical contacts.
U.S. Pat. No. 5,421,084 discloses an intermediate material for the production of electrical contacts, especially relay contacts. This intermediate material is also designed as a metal strip with a contact area, and it is welded by resistance heating to an electrically conductive contact carrier, which also has an electrical conductivity of more than 15 m/(ohms.times.mm.sup.2), i.e., more than (15 S.times.10.sup.6)/m. The contact carrier consists essentially of copper. The surface of the metal strip opposite from the contact area has ridge-like projections to serve as welding bosses, which carry a coating consisting essentially of silver for welding to the carrier. The melting point of this coating material is below the melting point of the metal strip, which consists essentially of nickel. The contact area itself is based on a gold alloy or a silver-palladium alloy.
As part of the trend toward the miniaturization of components and their associated contacts, it has been found difficult to provide several rows of parallel projections.